Hi Peter, etc, This little series tightens up rdpmc permissions. With it applied, rdpmc can only be used if a perf_event is actually mmapped. For now, this is only really useful for seccomp.
At some point this could be further tightened up to only allow rdpmc if an actual self-monitoring perf event that is compatible with rdpmc is mapped. (Is the current code there even correct? What happens if you set up a perf counter targetting a different pid and then try to rdpmc it? Do you end up reading the right value or does perf event context switching mess you up?) This should add <50ns to context switches between rdpmc-capable and rdpmc-non-capable mms. I suspect that this is well under 10% overhead, given that perf already adds some context switch latency. If needed, we could add a global switch that turns this behavior off. We could also rehink the logic. I think that patches 1-3 are a good idea regardless of any rdpmc changes. (Please don't apply quite yet, because there'll be a merge conflict with some changes that haven't landed yet. This is against 3.17.) Andy Lutomirski (5): x86: Clean up cr4 manipulation x86: Store a per-cpu shadow copy of CR4 x86: Add a comment clarifying LDT context switching perf: Add pmu callbacks to track event mapping and unmapping x86,perf: Only allow rdpmc if a perf_event is mapped arch/x86/include/asm/mmu.h | 2 + arch/x86/include/asm/mmu_context.h | 30 +++++++++++++- arch/x86/include/asm/processor.h | 33 ---------------- arch/x86/include/asm/tlbflush.h | 77 ++++++++++++++++++++++++++++++++---- arch/x86/include/asm/virtext.h | 3 +- arch/x86/kernel/cpu/common.c | 17 +++++--- arch/x86/kernel/cpu/mcheck/mce.c | 3 +- arch/x86/kernel/cpu/mcheck/p5.c | 3 +- arch/x86/kernel/cpu/mcheck/winchip.c | 3 +- arch/x86/kernel/cpu/perf_event.c | 61 +++++++++++++++++++++------- arch/x86/kernel/head32.c | 1 + arch/x86/kernel/head64.c | 2 + arch/x86/kernel/i387.c | 3 +- arch/x86/kernel/process.c | 5 ++- arch/x86/kernel/xsave.c | 3 +- arch/x86/kvm/vmx.c | 8 ++-- arch/x86/mm/init.c | 12 +++++- arch/x86/mm/tlb.c | 3 -- arch/x86/xen/enlighten.c | 4 +- include/linux/perf_event.h | 7 ++++ kernel/events/core.c | 9 +++++ 21 files changed, 210 insertions(+), 79 deletions(-) -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
